1. Field of the Disclosure
The present disclosure relates to determining a downhole parameter of a formation and, in particular, to determining the downhole parameter using a current flowing through a drill string as a result of a spontaneous potential of the formation.
2. Description of the Related Art
Petroleum exploration involves drilling a borehole through one or more formations of the earth using a drill string with a drill bit at one end. The drill string traverses the formation as the drill bit disintegrates formation. The drill string may include conductive elements, such as a drill collar of the drill string and a wash pipe interior to the drill collar. The drill collar and wash pipe are generally electrically coupled to the formation and current may thus flow through the drill string. The magnitude of the current is generally related to a spontaneous potential that is in the formation and which is determined, in part, by various parameters of the formation.